The present invention relates to transfer members useful in electrostatographic reproducing apparatuses, including digital, image on image and contact electrostatic printing apparatuses. The present transfer members can be used as intermediate transfer members, transfuse or transfix members, transport members, and the like. The transfer members are useful, in embodiments, in liquid ink development applications. In a preferred embodiment, the transfer members comprise a low surface energy release agent such as a polydimethylsiloxane release agent.
In a typical electrostatographic reproducing apparatus such as electrophotographic imaging system using a photoreceptor, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of a developer mixture. One type of developer used in such printing machines is a liquid developer comprising a liquid carrier having toner particles dispersed therein. Generally, the toner is made up of resin and a suitable colorant such as a dye or pigment. Conventional charge director compounds may also be present. The liquid developer material is brought into contact with the electrostatic latent image and the colored toner particles are deposited thereon in image configuration.
The developed toner image recorded on the imaging member is transferred to an image receiving substrate such as paper via an intermediate transfer member. The toner particles may be transferred by heat and/or pressure to an intermediate transfer member, or more commonly, the toner image particles may be electrostatically transferred to the intermediate transfer member by means of an electrical potential between the imaging member and the intermediate transfer member. After the toner has been transferred to the intermediate transfer member, it is then transferred to the image receiving substrate, for example by contacting the substrate with the toner image on the intermediate transfer member under heat and/or pressure.
Intermediate transfer members enable high throughput at modest process speeds. In four-color photocopier systems, the intermediate transfer member also improves registration of the final color toner image. In such systems, the four component colors of cyan, yellow, magenta and black may be synchronously developed onto one or more imaging members and transferred in registration onto an intermediate member at a transfer station.
In electrostatographic printing machines in which the toner image is transferred from the intermediate transfer member to the image receiving substrate, it is important that the transfer of the toner particles from the intermediate transfer member to the image receiving substrate be substantially 100 percent. Less than complete transfer to the image receiving substrate results in image degradation and low resolution. Completely efficient transfer is particularly important when the imaging process involves generating full color images since undesirable color deterioration in the final colors can occur when the color images are not completely transferred from the intermediate transfer member.
Thus, it is important that the intermediate transfer member surface has excellent release characteristics with respect to the toner particles. Conventional materials known in the art for use as intermediate transfer members often possess the strength, conformability and electrical conductivity necessary for use as intermediate transfer members, but can suffer from poor toner release characteristics, especially with respect to higher gloss image receiving substrates.
Although use of a release agent increases toner transfer, the transfer member outer layer tends to swell upon addition of the release agent. For example, it has been shown that silicone rubber performs well as a transfer layer, but swells significantly in the presence of hydrocarbon fluid release agent. Also, release properties have been shown to decay from repeated interaction with certain release agents such as hydrocarbon release agents.
U.S. Pat. No. 5,459,008 discloses an intermediate transfer member in combination with a thin film coating of a release agent material comprising a polyolefin, a silicone polymer, or grafts of these polymers, and mixtures thereof.
A need remains for an intermediate transfer member that exhibits substantially 100 percent toner transfer, without system failure, to image receiving substrates having glosses ranging from low to very high. Further, a need remains for a combination of transfer member surface layer and release agent that does not result in significant swelling of the outer layer of the transfer member. In addition, it is desired to present a combination of transfer member layer and release agent in which the release properties of the transfer member do not significantly decay over repeated interaction with the release agent.